Because of the high heat and low humidity in the summer in Death Valley, California, a visitor requires about one quart of water for every two miles traveled on foot. If the density of water is 0.990 g/mL at 45°C, how many kilograms of water are required for a person to walk 30 kilometers in Death Valley?

The answer to your question is   mass = 8.73 kg

Step-by-step explanation:

Data

1 quart 2 mi

density = 0.99 g/ml

total distance = 30 km

Process

1.- Convert 2 mi to km

                  1 mi 1.61 km

                  2 mi  x

                  x = (2 x 1.61)/1

                  x = 3.22 km

2.- Calculate the quarts drank

                   1 quart 3.22 km

                   x           30 km

                   x = (30 x 1)/3.22

                   x = 9.32 quarts

3.- Convert quarts to milliliters

                   1 quart 946.35 ml

                 9.32 quart x

                  x = (9.32 x 946.35) / 1

                  x = 8817 ml

4.- Calculate the grams of water

     density = mass / volume

     mass = volume x density

-Substitution

     mass = 8817 x 0.99 g/ml

-Result

     mass = 8729 g

5.- Convert to kg

     mass = 8729/1000 kg

     mass = 8.73 kg

the value of v.w= -12.

step-by-step explanation:

we are given three vector r,v and w as:

r = < 5, -5, -2> ; v = < 2, -8, -8> ; w = < -2, 6, -5>

we know that r,v and w could also be represented as:

r=5i-5j-2k

v=2i-8j-8k

and w= -2i+6j-5k

where i,j and k are the unit vectors of x,y and z-axis respectively.

also we know that it has the following property:

i.i=1 ; j.j=1; k.k=1

and i.=j.i=i.k=k.i=j.k=k.j=0

i.e. when we multiply two vectors or we find it's dot product we need to only multiply the components of x coordinates with each other; y with each other and z with each other.

hence, v.w= (2i-8j- -2i+6j-5k)

                  = 2×(-2)+(-8)×(6)+(-8)×(-5)

                  = -4-48+40

                  = -12

hence, v.w= -12

it is a. 4.2 because 7.6-3.4 gets the remaining length of 4.2. i might be wrong but i am pretty sure this is the answer.